Table 3 Outcome measure definitions

Primary outcome

Effectiveness of pain relief from randomisation to arrival at hospital as measured by Sum of Pain Intensity Difference (SPID) score (using a 0–10 numerical rating scale)

The SPID is measured using a weighted sum of the scores, as shown below:

\(SPID_{n} = \mathop \sum \limits_{i - 1}^{n} \left( {T_{i} - T_{i - 1} } \right)*PID_{i}\)

T_i is the time in hours when observation i is taken

PID_i is the difference in Pain Intensity (PI) scores from initial pain score to the pain score at time T_i. The SPID looks to calculate the area under the curve of pain intensity different over time

Secondary outcomes

The Total Pain Relief (TOTPAR)

The TOTPAR is measured using a weighted sum of the scores, as shown below:

\({TOTPAR}_{n}= \sum_{i-1}^{n}\left({T}_{i}-{T}_{i-1}\right)*{PAR}_{i}\)

T_i is the time in hours when observation i is taken

PAR_i is the pain relief score measured as defined below on a scale of 1 to 3

We measure minimal pain relief as 1.8 (1.7–1.9) change in pain score, much pain relief as 4.0 (3.9–4.1) and very much pain relief as 5.2 (5–5.4)

Percentage changes defined as

20.3 (19–21.6), 44.4 (43.2–45.6), 56.1 (53.9–58.4) respectively

Time to Perceptible Analgesia

Perceptible pain relief is defined as a 20% change in NRS pain score from the initial pain score. The time will be taken as time of perceptible analgesia minus time of first administration

If 20% change not achieved, we will score this as perceptible analgesia not achieved

Time to Meaningful Analgesia

Defined as a 44% change in NRS pain score from initial pain score. The time will be taken as time of meaningful analgesia minus time of first administration

If 44% change not achieved, we will score this as meaningful analgesia not achieved

Time to Peak Analgesia

Measured as the time when lowest NRS pain score, relative to initial pain score, is achieved minus time of first administration

Duration of Analgesia

Measured as the time period in which patient pain scores have consecutively decreased or remained stationary (There may be different instances of this per patient)

Requirement for Rescue Analgesia

We will record whether a patient has needed rescue analgesia and which analgesia was administered, Entonox, paracetamol, ibuprofen, or other

Proportion of patients with pain intensity score below 4/10 on NRS scale

At hospital arrival the research paramedic will record a NRS pain score. We will provide the proportion, as a percentage, of each patient that achieved a score < 4/10

If there is no hospital arrival score, we will use the scores recorded in the ambulance journey

Vital Signs

At each observation time, the respiratory rate (bpm), oxygen saturations (%), heart rate (bpm), blood pressure (mmHg) and their Glasgow Coma Scale (GCS)

Glasgow Coma Scale

Three subscales measuring eyes, verbal, and motor response of each patient. The scales are as such:

Eyes 1–4

Verbal 1–5

Motor 1–6

Global Impression of Change

Using a 7-point Likert scale. The options offered ranging from ‘very much improved’ to ‘very much worse’

Side effects and adverse events

Measured in the following categories, ‘Airway’, ‘Respiratory’, ‘Cardiovascular’, ‘Neurologic’, and ‘other’

Ambulance job cycle time

Time taken from arrival on scene to hospital arrival

Number of ambulance resources

Number of doctors, paramedics, doctors, and vehicles attending scene

Cumulative IMP doses administered

Total dose of IMP administered

CT scan use

If patient had a CT scan and how many

Hospital or ICU admission

Yes; no option if patient is admitted to hospital or ICU

Length of stay in ED, ICU, or hospital

Classed as date and time of admission to date and time of discharge

BPI-SF at 3 and 6 Months

9 part self-reported form which allows us to monitor the severity of the patient’s pain and its effect on their daily life. Split into two sections, pain intensity and pain inference

9 part self-reported form which allows us to monitor the severity of the patient’s pain and its effect on their daily life

Pain Intensity

The pain severity part assesses the pain of the patient at its worst, least, average and now

We can then determine the average of the 4 categories to determine pain intensity, however it is recommended that we present all 4 of the options

Pain Interference

The interference section measures the effect of pain in 7 different tasks, walking, work, mood, enjoyment of life, relations with others, and sleep

Measure as a mean if at least 4 of the sections have been completed